N-glycolylneuraminic Acid (Neu5Gc) is an antigenic non-human sialic acid found on cells of many mammals. Earlier studies suggested that Neu5Gc, which cannot be produced by humans due to a genetic defect, is an "oncofetal antigen", and that patients with cancer express antibodies against it. Since then, it has been found that all humans express variable levesl of a complex polyclonal antibody response against a variety of Neu5Gc-containing glycans, and that levels are elevated in humans diagnosed with some cancers. Knowing the anti-Neu5Gc antibody profile of a patient may prove to be of diagnostic andlor prognostic value, especially if an anti-Neu5Gc profile is characteristic for certain forms of cancer. Modification of current microarray technologies facilitated the creation of a sialic acid glycan microarray that is useful in the rapid identification of anti-Neu5Gc antibody profiles. Our Phase I work showed feasibility, and suggested that such serum anti-Neu5Gc antibody profiles have the potential for sensitivity, specificity and reproducibility. This Phase Ii proposal will expand and optimize the array approach, with the ultimate goal of identifying and validating a particular anti-Neu5Gc antibody profile that is predictive of cancer risk, diagnosis andlor prognosis, and that can subsequently be commercialized.